A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. Such a lithographic apparatus is described in US 2003/0048960 A1. This lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to impart a beam of radiation with a pattern in its cross-section, the pattern corresponding to a circuit pattern to be formed on an individual layer of the IC. This pattern can be imaged or transferred onto a target portion (e.g. comprising part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. In the known lithographic apparatus each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.
In the known lithographic apparatus the patterning device is coupled to the support structure by a supporting device. The supporting device is provided with a clamp area (e.g. a vacuum clamp) to hold the patterning device in place with respect to the support structure.
US 2003/0048960 A1 describes that there is a continuously increasing demand on higher accuracy in combination with higher throughput. In order to increase throughput, it is desirable to increase scan velocities, which consequently lead to higher scan accelerations and decelerations.
These higher accelerations and decelerations yield in an increased patterning device (nano) slip.
US 2003/0048960 A1 suggests additional linear encoder patterns, which are provided on the patterning device (e.g. reticle or mask). These encoder patterns are used for detecting relative displacement between the patterning device (e.g. mask or reticle) and the patterning device stage or support (e.g. reticle stage). This relative displacement is further used by a correction device to correct the position of e.g. the patterning device stage.
In the lithographic apparatus described in US 2003/0048960 A1, the linear encoder patterns are fixed to the patterning device. This is undesirable as only dedicated lithographic apparatus can cooperate with these devices.